Known in the prior art are aircraft wheel and brake assemblies including a non-rotatable wheel support, a wheel mounted to the wheel support for rotation, and a brake disk stack having front and rear axial ends and alternating rotor and stator disks mounted with respect to the wheel support and wheel for relative axial movement. Each rotor disk is coupled to the wheel for rotation therewith and each stator disk is coupled to the wheel support against rotation. A back plate is located at the rear end of the disk pack and a brake head is located at the front end. The brake head houses a plurality of actuators that extend to compress the brake disk stack against the back plate. Torque is taken out by the stator disks through a static torque tube or the like.
Each stator disk includes a friction material that engages the rotor disk as the brake disk stack is compressed, thereby converting kinetic energy into heat energy. As a result of the conversion process, the friction material undergoes wear and, thus, the friction material requires periodic maintenance to determine if the friction material is worn out or otherwise requires replacement.
Friction material wear occurs not only when the brakes are applied during a landing stop of an aircraft, but also when the brakes are applied during a taxi stop. In many instances, a taxi stop subjects the friction material to more wear than landing stops.
Present day brake systems have employed wear pin indicators to measure overall wear of friction material in a brake disk stack. In such systems, brake wear is indicated, for example, by the length of the pin relative to a reference plate. This arrangement requires a visual inspection of the pin to determine wear and is inherently imprecise.
U.S. Pat. No. 7,108,107 to Ralea provides a system for electrically measuring brake wear in a brake actuator assembly. As the brake disks wear, the collective axial thickness thereof will decrease. The system includes an electric transducer which detects a change in the thickness of the brake stack in order to provide an indication of brake wear.